Does gestation vary by ethnic group? A London-based study of over 122,000 pregnancies with spontaneous onset of labour

BACKGROUND: Evidence exists that normal gestational length varies with ethnicity. This UK-based study compares gestational length amongst a cohort of white European, Black and Asian women. METHODS: The cohort comprised 122 415 nulliparous women with singleton live fetuses at the time of spontaneous labour, giving birth in the former North West Thames Health Region, London, UK. RESULTS: The median gestational age at delivery was 39 weeks in Blacks and Asians and 40 weeks in white Europeans. Black women with normal body mass index (BMI) (18.5-24.9 kg/m(2)) had increased odds of preterm delivery (odds ratio [OR] = 1.33, 95% CI: 1.15, 1.56, adjusted for deprivation and BMI) compared with white Europeans. The OR of preterm delivery was also increased in Asians compared with white Europeans (OR = 1.45, 95% CI: 1.33, 1.56, adjusted for single unsupported status and smoking). Meconium stained amniotic fluid, which is a sign of fetal maturity, was statistically significantly more frequent in preterm Black and Asian infants and term Black infants compared with white European infants. CONCLUSIONS: This research suggests that normal gestational length is shorter in Black and Asian women compared with white European women and that fetal maturation may occur earlier.     

Body size and breast cancer risk in black women and white women: the Carolina Breast Cancer Study

The relation between body size and breast cancer risk was investigated in a population-based, case-control study of Black women (350 cases, 353 controls) and White women (523 cases, 471 controls) from North Carolina, aged 20-74 years in 1993-1996. Logistic regression analyses compared tertiles of each body size variable, adjusting for age and breast cancer risk factors (results shown for highest relative to lowest tertile). Among premenopausal women, body mass index (kg/m2) was inversely associated with breast cancer (odds ratio (OR) = 0.46, 95% confidence interval (CI): 0.26, 0.80) for Whites but not for Blacks. There was essentially no association among postmenopausal women. Higher waist/hip ratio, adjusted for body mass index, increased risk for all women. Odds ratios for Black and White premenopausal women were 2.50 (95% CI: 1.10, 5.67) and 2.44 (95% CI: 1.17, 5.09), respectively; odds ratios for Black and White postmenopausal women were 1.62 (95% CI: 0.70, 3.79) and 1.64 (95% CI: 0.88, 3.07), respectively. Findings for body mass index differed among Black women when stratified by age (<50 years) (OR = 0.50, 95% CI: 0.25, 1.01) instead of menopausal status. Thus, the associations of breast cancer with body mass index and waist/hip ratio among Black women are similar to those documented for Whites, despite different body size profiles on average.     

Obesity, gestational weight gain and preterm birth: a study within the Danish National Birth Cohort

The aim of the present study was to assess the impact of obesity and gestational weight gain on the risk of subtypes of preterm birth, because little is known about these associations. The study included 62 167 women within the Danish National Birth Cohort for whom self-reported information about prepregnancy body mass index (BMI) and gestational weight gain was available. Information about spontaneous preterm birth with or without preterm premature rupture of membranes (PPROM) and about induced preterm deliveries was obtained from national registers. Cox regression analyses were used to examine associations of prepregnancy BMI and gestational weight gain with subtypes of preterm birth. The crude risks of PPROM and of induced preterm deliveries were higher in obese women (BMI > or = 30) than in normal-weight women (18.5 < or = BMI < 25), especially before 34 completed weeks of gestation, when obese women faced twice the risk. In the adjusted analysis, the hazard ratios and 95% confidence intervals for PPROM and for induced preterm delivery in obese women were 1.5 [1.2, 1.9] and 1.2 [1.0, 1.6] respectively. When obesity-related diseases were accounted for, no excess risk of induced preterm deliveries was seen in obese women, but the increased risk of PPROM was unchanged. Low weight gain was associated with an increased risk of all subtypes of preterm birth compared with normal weight gain, especially in early spontaneous preterm births, where the risk was doubled. We concluded that prepregnancy obesity was associated with a higher risk of PPROM and early induced preterm deliveries.     

Neighborhood deprivation and preterm birth among non-Hispanic Black and White women in eight geographic areas in the United States

Disparities in preterm birth by race and ethnic group have been demonstrated in the United States. Recent research has focused on the impact of neighborhood context on racial disparities in pregnancy outcomes. The authors utilized vital-record birth certificate data and US Census data from eight geographic areas in four states (Maryland, Michigan, North Carolina, and Pennsylvania) to examine the relation between neighborhood deprivation and preterm birth among non-Hispanic White and Black women. The years covered by the data varied by site and ranged from 1995 to 2001. Results were adjusted for maternal age and education, and specific attention was paid to racial and geographic differences in the relation between neighborhood deprivation and preterm birth. Preterm birth rates were higher for non-Hispanic Blacks (10.42-15.97%) than for non-Hispanic Whites (5.77-9.13%), and neighborhood deprivation index values varied substantially across the eight areas. A significant association was found between neighborhood deprivation and risk of preterm birth; for the first quintile of the deprivation index versus the fifth, the adjusted summary odds ratio was 1.57 (95% confidence interval: 1.41, 1.74) for non-Hispanic Whites and 1.15 (95% confidence interval: 1.08, 1.23) for non-Hispanic Blacks. In this study, deprivation at the neighborhood level was significantly associated with increased risk of preterm birth among both non-Hispanic White women and non-Hispanic Black women.     

Chemical hair treatments and adverse pregnancy outcome among Black women in central North Carolina

Several studies suggest that toxic chemicals in hair products may be absorbed through the scalp in sufficient amounts to increase the risks of adverse health effects in women or their infants. This case-control study of 525 Black women from three counties in North Carolina who had delivered a singleton, liveborn infant examined whether exposure to chemicals used in hair straightening and curling increased the odds that the infant was preterm or low birth weight. Cases consisted of 188 preterm and 156 low birth weight births (for 123 women, their infant was both low birth weight and preterm). Controls were 304 women who delivered term and normal birth weight infants. Women who used a chemical hair straightener at any time during pregnancy or within 3 months prior to conception had an adjusted odds ratios (OR) of 0.7 (95% confidence interval (CI) 0.4-1.1) for preterm birth and 0.6 (95% CI 0.4-1.1) for low birth weight. Exposure to chemical curl products was also not associated with preterm delivery (adjusted OR = 0.9, 95% CI 0.5-1.8) or low birth weight (adjusted OR = 1.0, 95% CI 0.5-1.9). Despite this failure to find an association, continued search for risk factors to which Black women are uniquely exposed is warranted.     

Vaginal bleeding during pregnancy and preterm birth

This study investigated the relation between self-reported vaginal bleeding during pregnancy and preterm birth in a prospective cohort of 2,829 pregnant women enrolled from prenatal clinics between 1995 and 2000 in central North Carolina. The overall association between vaginal bleeding and preterm birth was modest (risk ratio (RR) = 1.3, 95% confidence interval (CI): 1.1, 1.6). Bleeding in the first trimester only was associated with earlier preterm birth (< or =34 weeks' gestation) (RR = 1.6, 95% CI: 1.1, 2.4) and preterm birth due to preterm premature rupture of the membranes (PPROM) (RR = 1.9, 95% CI: 1.1, 3.3). Bleeding in both trimesters was associated with preterm birth due to preterm labor (RR = 3.6, 95% CI: 1.9, 6.8). Bleeding of multiple episodes, on multiple days, and with more total blood loss was associated with an approximate twofold increased risk of earlier preterm birth, PPROM, and preterm labor. In contrast, bleeding in the second trimester only, of a single episode, on a single day, and with less total blood loss was not associated with any category of preterm birth. Vaginal bleeding was not associated with preterm birth among African Amercians (RR = 1.2, 95% CI: 0.9, 1.7). This study indicates that more intense but not less intense bleeding is associated with earlier preterm birth and spontaneous preterm birth presenting as PPROM or preterm labor, and it suggests that bleeding is less predictive of preterm birth among African-American compared with White women.     

Maternal prepregnancy weight and congenital heart defects in offspring.

To determine the relation between having an infant with a major heart defect and a mother's prepregnancy weight, we compared 1,049 Atlanta-area women who gave birth to liveborn or stillborn infants, each with a major heart defect, with 3,029 Atlanta-area women who gave birth to infants without birth defects. The infants of control women were randomly selected from birth certificates and were frequency-matched to the case group by race, birth hospital, and birth period from 1968 through 1980. After excluding diabetic mothers and adjusting for potential confounders, compared with average-weight women (body mass index 19.9--22.7), we found that underweight women (body mass index <16.5) were less likely to have a child with a major isolated heart defect [odds ratio (OR) = 0.64; 95% confidence interval (CI) = 0.43--0.97], whereas the OR was elevated among overweight or obese women (body mass index >26) (OR = 1.36; 95% CI = 0.95--1.93). Using average-weight women who did not take periconceptional multivitamins as the reference group, periconceptional multivitamin use was associated with a reduced OR for isolated heart defects among average-weight women (OR = 0.61, 95% CI = 0.36--0.99) and underweight women but not among overweight or obese women (OR = 1.69, 95% CI = 0.69--3.84).     

Role of anxiety and depression in the onset of spontaneous preterm labor

The aim of this cohort study conducted in France in 1997-1998 was to investigate the effects of antenatal anxiety and depression on spontaneous preterm labor. A consecutive series of 634 pregnant women with singleton pregnancies was included. Anxiety and depression were assessed using self-administered questionnaires: Spielberger's State-Trait Anxiety Inventory and the Edinburgh depression scale. Depression scores were dichotomized with a cutoff value suggestive of major depression. The 75th percentile was used for anxiety scores. A logistic regression analysis, controlling for sociodemographic and biomedical factors and including interaction terms, revealed that depression was positively associated with the outcome among underweight women, defined as women with a prepregnancy body mass index below 19 (adjusted odds ratio (OR) = 6.9, 95% confidence interval (CI): 1.8, 26.2). A similar result was observed for trait anxiety in women with a history of preterm labor (adjusted OR = 4.8, 95% CI: 1.1, 20.4). The association was close to significance for state anxiety in women with vaginal bleeding (adjusted OR = 3.6, 95% CI: 0.9, 14.7). These findings show that anxiety and depression, when combined with specific biomedical factors, are associated with spontaneous preterm labor. A synergic action of psychological and biomedical factors on the secretion of placental corticotropin-releasing factor is hypothesized.     

The preterm prediction study: the value of new vs standard risk factors in predicting early and all spontaneous preterm births. NICHD MFMU Network.

OBJECTIVES: This study was undertaken to determine the relationship between fetal fibronectin, short cervix, bacterial vaginosis, other traditional risk factors, and spontaneous preterm birth. METHODS: From 1992 through 1994, 2929 women were screened at the gestational age 22 to 24 weeks. RESULTS: The odds ratios for spontaneous preterm birth were highest for fetal fibronectin, followed by a short cervix and history of preterm birth. These factors, as well as bacterial vaginosis, were more strongly associated with early than with late spontaneous preterm birth. Bacterial vaginosis was more common--and a stronger predictor of spontaneous preterm birth--in Black women, while body mass index less than 19.8 was a stronger predictor in non-Black women. This analysis suggests a pathway leading from Black race through bacterial vaginosis and fetal fibronectin to spontaneous preterm birth. Prior preterm birth is associated with spontaneous preterm birth through a short cervix. CONCLUSIONS: Fetal fibronectin and a short cervix are stronger predictors of spontaneous preterm birth than traditional risk factors. Bacterial vaginosis was found more often in Black than in non-Black women and accounted for 40% of the attributable risk for spontaneous preterm birth at less than 32 weeks.     

Low preconception body mass index is associated with birth outcome in a prospective cohort of Chinese women

Low maternal prepregnancy BMI is associated with adverse birth outcomes, but the BMI at which risk increases is not well defined. We assessed whether the relationship between prepregnancy BMI and birth outcomes is influenced by the extent to which mothers were underweight in a prospective study in Anhui, China. The women (n = 575) were 20-34 y old, married, nulliparous and nonsmokers. All measures of infant growth increased with increasing maternal BMI until a plateau was reached at a BMI of 22-23 kg/m2. Infants born to the 27% of women who were severely underweight before pregnancy (BMI < or = 18.5 kg/m2) were at increased risk for fetal growth deficits associated with infant morbidity. Compared with a normal BMI, being severely underweight was associated with mean (+/- SEM) reductions of 219 +/- 40 g in infant birthweight and 6.7 +/- 1.3% in the birthweight ratio and an 80% increase in risk of intrauterine growth restriction [odds ratio (OR) 1.8; 95% CI: 1.0, 3.3; P = 0.05]. Being severely underweight was also associated with smaller infant head circumference and lower ponderal index. Being moderately underweight (18.5 < BMI < 19.8 kg/m2) was not significantly associated with adverse pregnancy outcomes. Gestational age and risk of preterm birth were not associated with maternal BMI. More than half of the women in this study were underweight before pregnancy. Although being moderately underweight was not associated with increased risk of adverse pregnancy outcomes, being severely underweight was an important risk factor for reduced fetal growth.     

Obesity and gestational weight gain: cesarean delivery and labor complications

OBJECTIVE: To assess the association between pre-gestational obesity and weight gain with cesarean delivery and labor complications. METHODS: A total of 4,486 women 20-28 weeks pregnant attending general prenatal care clinics of the national health system in Brazil from 1991 to 1995 were enrolled and followed up through birth. Body mass index categories based on prepregnancy weight and total weight gain were calculated. Associations between body mass index categories and labor complications were adjusted through logistic regression analysis. RESULTS: Obesity was present in 308 (6.9%) patients. Cesarean delivery was performed in 164 (53.2%) obese, 407 (43.1%) pre-obese, 1,045 (35.1%) normal weight and 64 (24.5%) underweight women. The relative risk for cesarean delivery in obese women was 1.8 (95% CI: 1.5-2.0) compared to normal weight women. Greater weight gain was particularly associated with cesarean among the obese (RR 4th vs 2nd weight gain quartile 2.2; 95% CI: 1.4-3.2). Increased weight at the beginning of pregnancy was associated with a significantly higher adjusted risk of meconium with vaginal delivery and perinatal death and infection in women submitted to cesarean section. Similarly, greater weight gain during pregnancy increased the risk for meconium and hemorrhage in women submitted to vaginal delivery and for prematurity with cesarean. CONCLUSIONS: Pre-gestational obesity and greater weight gain independently increase the risk of cesarean delivery, as well as of several adverse outcomes with vaginal delivery. These findings provide further evidence of the negative effects of prepregnancy obesity and greater gestational weight gain on pregnancy outcomes.     

Gestational vaginal bleeding and pregnancy outcome

The relation between vaginal bleeding and pregnancy outcome was examined in a prospective study of 3,531 women seeking prenatal care in New York City from 1975 through 1985. Women were interviewed in the second trimester or later and were followed up at delivery. The frequency of vaginal bleeding during pregnancy was 22%. Few maternal characteristics or exposures were predictive of bleeding, and those that were associated with an increased risk of bleeding were only marginally so. Risk factors included advanced maternal age, previous spontaneous or induced abortion, working during pregnancy, and certain gynecologic conditions (fibroids, cervical inflammation, and ovarian cysts). Severity of bleeding was examined in relation to birth weight and length of gestation at delivery. Light bleeding during pregnancy was not associated with decreased birth weight or with shortened gestation at delivery. Heavy bleeding was associated with a decrease in mean birth weight of about 100 g (p less than 0.05) but was not significantly associated with the risk of low birth weight (odds ratio (OR) = 1.7, 95% confidence interval (CI) 0.9-3.3). Heavy bleeding was associated with preterm delivery among private patients (OR = 6.4, 95% Cl 1.7-23.5) but not public patients (OR = 0.3, 95% Cl 0.1-1.4). First trimester bleeding of any severity was marginally associated with congenital malformations in the offspring (OR = 1.7, 95% Cl 1.0-2.9); the effect was the same for major and minor abnormalities. There was no association between first trimester bleeding and placental complications of pregnancy or the delivery of a stillborn infant.     

Adult weight change, weight cycling, and prepregnancy obesity in relation to risk of preeclampsia

BACKGROUND: Preeclampsia has been shown to be associated with obesity, with other risk factors for cardiovascular disease, and with subsequent cardiovascular disease itself. However, the possible association with weight gain and weight cycling has not been evaluated. METHODS: In this prospective study of a cohort of 1644 pregnant women, we assessed adult weight change, intentional weight cycling, and prepregnancy obesity in relation to preeclampsia risk. Net weight change from age 18 years to the period 3 months before conception was determined for each participant. Weight cycling was defined as intentional weight loss and unintentional regain of at least 15 pounds during periods not related to pregnancy or lactation. We used multivariate regression procedures to calculate risk ratios (RRs) and 95% confidence intervals (CIs). RESULTS: Relative to women with stable weight (gained or lost < 2.5 kg) women who gained 5.0-9.9 kg experienced a 2.6-fold increased risk of preeclampsia (95% CI = 1.0-6.7). The corresponding risk ratio (RR) for women who gained > or = 10 kg was 5.1 (2.2-12.2). Intentional weight cycling, after controlling for weight at age 18 years, adult weight change, and other risk factors, was not associated with increased risk of preeclampsia (RR = 1.1; CI = 0.6-1.8). RRs increased monotonically with increasing prepregnancy body mass index greater than 19.8 kg/m. After adjusting for confounders, the RR for prepregnancy overweight women and obese women were 1.7 (0.6-4.9) and 3.4 (1.5-7.6) respectively. CONCLUSIONS: These results suggest that adult weight gain and prepregnancy overweight and obesity status are associated with an increased risk of preeclampsia.     

早产发生的影响因素及其流行病学研究进展

  目的  探究中国西部地区妊娠期糖尿病与早产发生风险的关系。  方法  连续纳入2013年10月 — 2014年2月在四川大学华西第二医院门诊部进行产前保健的1 962名孕晚期孕妇,收集孕妇基本特征、孕妇生育史和孕期疾病特征等资料,使用logistic回归模型分析妊娠期糖尿病对早产发生风险的独立作用。  结果  共419名孕妇罹患妊娠期糖尿病,38人发生早产。单因素分析发现,妊娠期糖尿病与早产的发生相关（P = 0.019）。多因素logistic回归分析显示,在控制相关协变量后,妊娠期糖尿病患者发生早产的风险是正常孕妇的2.17倍（OR = 2.17,95 % CI = 1.09～4.34,P = 0.028）。亚组分析和敏感性分析的结果较为稳定。  结论  孕妇罹患妊娠期糖尿病可增加早产的发生风险,应积极控制妊娠期糖尿病患者的血糖和其他危险因素,以降低早产的发生率。     

Very low maternal lead level in pregnancy and birth outcomes in an eastern Massachusetts population

PurposeMaternal lead exposure is associated with poor birth outcomes in populations with moderate to high blood levels. However, no studies have looked at exposure levels commonly experienced by US women.MethodsWe evaluated the relationship between maternal red blood cell (RBC) lead levels in midpregnancy and birth outcomes in 949 mother–child pairs in a prebirth cohort. We used multiple linear regression and logistic regression, adjusted for potential confounders including maternal age, race, prepregnancy body mass index, and smoking to relate maternal lead to infant birth size and risk for preterm birth (<37 weeks).ResultsMean RBC lead level was 1.2 μg/dL (range, 0.0–5.0). Mean (standard deviation) birthweight was 3505 (520) g, birthweight for gestational age z-score 0.22 (0.93), and length of gestation 39.5 (1.7) weeks. Mothers in the highest versus lowest lead quartile did not have higher odds (OR, 1.85; 95% confidence interval [CI], 0.79–4.34) of preterm delivery; after stratifying by child sex, there was an association among males (OR, 5.51; 95% CI, 1.21–25.15) but not females (OR, 0.82; 95% CI, 0.24–2.85). Maternal RBC lead was not associated with any continuous outcomes in combined or sex-stratified analyses.ConclusionsMaternal lead exposure, even at very low levels, may adversely affect some childbirth outcomes, particularly preterm birth among males.     

Vitamin C and the risk of preeclampsia--results from dietary questionnaire and plasma assay

BACKGROUND: Oxidative stress plays an important role in the pathophysiology of preeclampsia. METHODS: In a case-control study of 109 women with preeclampsia and 259 controls, maternal dietary and plasma vitamin C in relation to preeclampsia risk were assessed. Dietary intake during the periconceptional period and pregnancy was ascertained using a semiquantitative food frequency questionnaire. Logistic regression procedures were used to derive odds ratios (OR) and 95% confidence intervals (CI). Plasma ascorbic acid was determined using automated enzymatic procedures. RESULTS: After adjusting for maternal age, parity, prepregnancy body mass index, and energy intake, women who consumed <85 mg of vitamin C daily (below the recommended dietary allowance), as compared with others, experienced a doubling in preeclampsia risk (OR = 2.1; 95% CI = 1.1-3.9). The OR for extreme quartiles of plasma ascorbic acid (<42.5 vs > or = 63.3 micromol/liter) was 2.3 (95% CI = 1.1-4.6). Compared with women in the highest quartile, those with plasma ascorbic acid <34.6 micromol/liter (lowest decile) experienced a 3.8-fold increased risk of preeclampsia (95% CI = 1.7-8.8). CONCLUSIONS: Our results, if confirmed, would suggest that current public health efforts to increase intake of fruits and vegetables rich in vitamin C and other antioxidants may reduce the risk of preeclampsia.     

Inflammation and dyslipidemia related to risk of spontaneous preterm birth

Women who deliver preterm are at increased risk for cardiovascular disease, but mechanisms are not understood. The authors considered that inflammation in women with spontaneous preterm birth (sPTB) might be related to their metabolic profile, such as lipids, and tested this in a nested case-control study from the Pregnancy Exposures and Preeclampsia Prevention Study (1997-2001). Cases were women with sPTB at 34-<37 weeks (n = 76) or < 34 weeks (n = 33). Controls were randomly selected women with term births (n = 228). Early pregnancy inflammation (C-reactive protein: > or = 8 microg/ml) and dyslipidemia (cholesterol: > 230 mg/dl or triglycerides: > 140 mg/dl) were evaluated in serum collected at < 21 weeks. Late pregnancy elevated C-reactive protein (> or = 12 microg/ml) was measured in a subset (n = 295). Polycotomous logistic regression was used to estimate the joint effects of C-reactive protein elevations and dyslipidemia on the risk of sPTB subtypes. After adjustment for race, body mass index, periconceptional vitamin use, and gestational age at sampling, early pregnancy inflammation (odds ratio = 2.9, 95% confidence interval (CI): 1.1, 7.2) and dyslipidemia (odds ratio = 2.0, 95% CI: 1.0, 4.2) were independently associated with sPTB at 34-<37 weeks. The presence of both conditions increased risk of sPTB at < 34 weeks 6.4-fold (95% CI: 1.7, 24.1). Half of the women with early pregnancy inflammation had elevated C-reactive protein late in gestation, and each was independently related to the risk of sPTB at < 34 weeks. The results indicate that some metabolic factors together with inflammation may be related to the risk of sPTB.     

Maternal and infant birth characteristics and hepatoblastoma

Hepatoblastoma is a rare embryonal tumor with unknown etiology. The authors conducted a case-cohort study using public health surveillance data sets to examine perinatal risk factors for hepatoblastoma. Hepatoblastoma cases (n = 58) diagnosed between 1985 and 2001 were identified from the New York State Cancer Registry and were matched to electronic birth records for 1985-2001 from New York State, excluding New York City. Controls (n = 6,056) were selected from the birth cohorts for the same years. Having a birth weight less than 1,000 g was associated with a strongly increased risk of hepatoblastoma (relative risk (RR) = 56.9, 95% confidence interval (CI): 24.0, 130.7). After adjustment for birth weight, a moderately increased risk of hepatoblastoma was found for younger maternal age (<20 years vs. 20-29 years: RR = 2.5, 95% CI: 1.0, 5.5), presumptive use of infertility treatment (RR = 9.2, 95% CI: 2.1, 31.5), maternal smoking (RR = 2.1, 95% CI: 1.0, 4.2), and higher maternal prepregnancy body mass index (body mass index of 25-29 vs. 20-24: RR = 2.9, 95% CI: 1.2, 7.6).     

Racial Differences in the Patterns of Singleton Preterm Delivery in the 1988 National Maternal and Infant Health Survey

Objectives: To determine if the association between race and preterm delivery would persist when preterm delivery was partitioned into two etiologic pathways. Methods: We evaluated perinatal and obstetrical data from the 1988 National Maternal and Infant Health Survey and classified preterm delivery as spontaneous or medically indicated. Discrete proportional hazard models were fit to assess the risk of preterm delivery for Black women compared with White women adjusting for potential demographic and behavioral confounding variables. Results: Preterm delivery occurred among 17.4% of Black births and 6.7% of White births with a Black versus White unadjusted hazard ratio (HR) of 2.8 (95% CI = 2.4–3.3). The adjusted HR for a medically indicated preterm delivery showed no racial difference in risk (HR = 1.0, 95% CI = 0.4–2.6). However, for spontaneous preterm delivery between 20 and 28 weeks gestation, the Black versus White adjusted hazard ratio (HR) was 4.9 (95% CI = 3.4–7.1). Conclusions: Although we found an increased unadjusted HR for preterm delivery among Black women compared with White women, the nearly fivefold increase in adjusted HR for the extremely preterm births and the absence of a difference for medically indicated preterm delivery was unexpected. Given the differences in the risks of preterm birth between Black and White women, we recommend to continue examining risk factors for preterm delivery after separating spontaneous from medically indicated preterm birth and subdividing preterm delivery by gestational age to shed light on the reasons for the racial disparity.     

Variation in mammographic breast density by race

PURPOSE: Because of the observed racial differences in risk of developing breast cancer, the authors conducted a study to determine the variation in breast density, a strong predictor of breast cancer risk, by race and age. METHODS: Study subjects were women enrolled in Group Health Cooperative of Puget Sound, Seattle, WA, aged 20-79 years, who had a screening mammogram between 6/1/96 and 8/1/97. Women with increased breast density (BI-RADS "heterogeneously dense" and "extremely dense") (n = 14,178) were compared to those with fatty breasts (BI-RADS "almost entirely fat" and "scattered fibroglandular tissue") (n = 14,323). Logistic regression was used with adjustment for age, parity, age at first birth, menopausal status, current use of hormone replacement therapy, and body mass index. RESULTS: The odds ratio (OR) for having dense breasts versus fatty breasts, comparing Asian to White women, increased from 1.2 [95% confidence interval (CI) 0.9-1.6] for women age <45 to 1.6 (95% CI 1.3-2.2) for women over 65. Conversely, the OR for Black compared to White women was highest for the women age 65 and younger (OR 1.7 (1.2-2.3), 1.3(1.0-1.7), and 1.7 (1.2-2.3) for women age <45, 46-55, and 56-65, respectively), whereas Black women over 65 had similar density as Whites. Hispanic women had similar density compared to Whites for all ages. CONCLUSIONS: These racial differences in breast density generally do not conform to differences in race and age-specific breast cancer incidence rates.